Catalysts for the oxidation of carbon monoxide and hydrocarbons, and for the reduction of nitrogen oxides of automobile exhaust emissions, are dispersed on washcoated metal or ceramic monoliths as automotive catalytic converters. Cerium oxide and/or cerium nitrate is usually mixed with gamma alumina to help improve catalytic performance, by providing oxygen under rich fuel conditions and is used also in a washcoat to increase dispersion of the metal catalysts, enhancing apparent catalytic activity. The surface area of gamma alumina decreases significantly during the aforementioned catalytic reactions at temperatures above about 600.degree. C. as the system ages. The result of this "washcoat sintering" is the loss of alumina surface area (and therefore adsorption sites for the metal catalyst) This results in a decrease of metal dispersion with a resultant lowering of catalytic activity.
It would be advantageous, to have a high surface area washcoated substrate which can function as a catalyst support at high temperatures without any significant loss of surface area and activity.
European Patent publication No. 0,292,167 B1 relates to an amorphous, refractory composition, its synthesis and use as a catalyst support for organic compound conversion reactions, particularly hydrotreating of petroleum residue. The composition is a combination of a rare earth oxide, aluminum oxide, and aluminum phosphate having a specified surface area and pore volume.